A sodium cooled fast reactor, which is one of alternatives of a fourth generation nuclear reactor that uses sodium as a coolant of a reactor, can enhance a nuclear fuel use rate, does not require a moderator or a high pressure within a nuclear reactor, and has excellent thermal efficiency, compared with an existing nuclear reactor.
However, sodium has a drawback in that it intensively reacts with water and oxygen, and combustion and explosion risk due to a strong exothermic chemical reaction require more resolute safety securement for both a cooling system and an energy conversion system, thereby weakening economic efficiency of a system. It is difficult to substantially apply sodium as a coolant due to a risk of such sodium.
According to a thesis (Jun-ichi Saito et al., “A study of atomic interaction between suspended nanoparticles and sodium atoms in liquid sodium”, Nuclear engineering and design, Vol. 240, p. 2664-2673, 2010) that was recently suggested in Japan in relation to such strong chemical activity of sodium, by appropriately matching nanoparticles with sodium, activity of the sodium can be reduced. According to the thesis, when well-dispersing nanoparticles in sodium in a liquid state, the nanoparticles have a surface area that is relatively larger than that of sodium atoms. When a large surface area of nanoparticles is formed with many unsaturated coupled atoms, the nanoparticles are easily coupled to sodium atoms due to high activity. The coupled atoms form a sodium-nanoparticle cluster to reduce reactivity with water.
In existing research, only studies concentrating on interaction of nanoparticles and sodium in terms of reactivity of sodium have been performed, but a basis of a sodium reaction is an oxidation-reduction process having an electron transfer process, and such a reaction generally passes through a very complex multi-step process, but a detailed mechanism thereof is not accurately understood. A reaction speed of sodium and water may be determined by a process (reduction) of generating hydrogen of an elemental state having high reactivity, as separated electrons react with water instead of a process (oxidation) in which electrons are separated from sodium. If nanoparticles can well “absorb” electrons, reactivity of electrons and water may be greatly reduced with only some nanoparticles. When a level in which nanoparticles of various metals like electrons is estimated through computational chemistry, a suggested possibility may be examined.
Metal nanoparticles can absorb electrons and show an affinity with hydrogen according to a property of a transition metal. A first aspect thereof is to disturb a process in which hydrogen is generated as electrons are absorbed by water molecules, a second aspect thereof is to disturb a process in which the generated hydrogen advances to explosion, and both of these aspects may contribute to reducing reactivity of a sodium metal.
However, up to now, an apparatus for dispersing nanoparticles in sodium of a liquid state has not been suggested, and an apparatus for dispersing nanoparticles and an experiment apparatus that is developed to continuously perform an experiment for determining reactivity of distributed sodium do not exist.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.